In a portable electronic device such as GPS (Global Positioning System) or wireless LAN (Local Area Network), it is required to combine a wireless technique and a high-density mounting technique. And therefore, a demand for mounting an analog semiconductor element and a digital semiconductor element so as to be close to each other or on one package is increasing. A technique for mounting an analog semiconductor element and a digital semiconductor element on the same board to integrate them in one module and a technique adopting an EBG (Electromagnetic Band Gap) layer as a ground plane of the board are described in “M.Swaminathan et al., “PowerDistribution Networks for System-on-Package: Status and Challenges”, IEEE Transactions on Advanced Packaging, Vol. 27, No. 2, May 2004” (Non-Patent Document 1).
And, there is a technique of reducing influence of mismatching of characteristic impedance caused by electromagnetic coupling generated between a signal through conductor and a grounding conductor layer having an opening arranged so as to surround the signal through conductor (for example, see Japanese Patent Application Laid-Open Publication No. 2004-259959 (Patent Document 1)).
Furthermore, there is a technique of relaxing mismatching of characteristic impedance at a connection portion between a signal wiring conductor and a signal through conductor and preventing noise interference between the signal wiring conductors (for example, see Japanese Patent Application Laid-Open Publication No. 2004-241426 (Patent Document 2)).